On a ship, it is desirable in some instances to provide more than one remote valve actuator for a remote control assembly. One such instance is in the case of a remotely controlled emergency fuel shut-off valve where it is desirable to have an actuator at several locations on board the ship, remote from the valve, so that during an emergency situation the valve may be actuated from any one of several locations about the ship.
Valve actuators of this type typically include at least one drive means, typically in the form of a handle, for manually actuating a core element. In the prior art motion transmitting remote control assemblies which include two or more actuators engaging a common core element, the handles of each actuator assembly are actuated in unison, i.e., as slaves, whenever the core element is moved. That is to say, when the handle of one actuator is moved to displace the core element, the handles of the additional actuators are also automatically moved due to their engagement with the one common core element.
An example of a prior art motion transmitting remote control assembly including two actuators engaging one common core element is shown in the U.S. Pat. No. 4,249,771 to Gergoe et al, issued Feb. 10, 1981. The Gergoe patent discloses two similar actuators including cable gears having peripherally disposed gear teeth which engage a helical thread extending along the core element. The Gergoe patent exemplifies the deficient state of the prior art in that movement of one of the actuator handles also moves the handle of the other remote actuator.
In many cases, it is desirable to lock the handle of an actuator assembly into a rest, i.e., unactuated, position. Under the teaching of the prior art, whenever one actuator handle is locked in position, all of the handles of the other actuator assemblies engaging the same core element become immoveably locked in place also. This situation is highly undesirable in applications where the core element actuates an emergency type system, such as an emergency fuel shut-off valve of a large ship. In such a situation, it is prudent to lock the handle into the unactuated position to prevent inadvertent actuation, although highly undesirable to require each individual actuator handle to be unlocked prior to actuating the emergency system.